1. Field of the Invention
The present invention relates to a method of manufacturing an active material used for a positive electrode of a secondary battery.
2. Description of the Related Art
In recent years, with an increase of environmental engineering, development of solar power generating technologies which pose less burden on the environment than conventional power generation methods has been actively conducted. Concurrently with the development of power generation technology, development of power storage technology has also been underway.
As a power storage technology, for instance, there is a lithium ion secondary battery (refer to Patent Documents 1 to 3). Lithium ion secondary batteries are widely prevalent since their energy density is high and because they are well suited for miniaturization. As a material used for a positive electrode of the lithium ion secondary battery, there is LiFePO4 of orthorhombic olivine structure, for example.
It was thought that LiFePO4 (lithium iron phosphate) of orthorhombic olivine structure would have favorable characteristics since the lithium (Li) is arranged one-dimensionally, but in actuality, for high speed charge and discharge, which is one of the characteristics required by a positive electrode material of a lithium ion secondary battery; when using the LiFePO4 crystal having the orthorhombic olivine structure in a positive electrode active material, the assumed characteristic value (theoretical capacity) was not long satisfied. Recently however, according to Kang et al., by controlling the size and the crystal surface of the LiFePO4 crystal, the characteristic value approximately equivalent to the theoretical capacity assumed in numerical calculation has been reportedly obtained (see Non-Patent Document 1).